Summary

A vulnerability in how Cisco ASA Software handles AnyConnect SSL VPN client connections could allow an unauthenticated, remote attacker to exhaust available memory which could cause the affected system to become unresponsive and transit traffic to be dropped.

The vulnerability is due to improperly clearing unused memory blocks after an AnyConnect SSL VPN client disconnects. An attacker could exploit this vulnerability by sending traffic to the IP address of the disconnected client.

Cisco has confirmed the vulnerability in a security advisory and released software updates.

Indicators of Compromise

Technical Information

The vulnerability is due to improper memory operations when processing AnyConnect SSL VPN client connections.

An unauthenticated, remote attacker could exploit the vulnerability by attempting to establish an AnyConnect VPN connection to a targeted device. The improper handling of the connection could cause the device to fail to release memory resources. The exhaustion of available memory resources due to repeated VPN connections could cause the device to become unresponsive, resulting in a DoS condition.

Analysis

Only devices that have enabled AnyConnect SSL VPN features are vulnerable to exploitation.

Safeguards

Administrators are advised to apply the appropriate updates.

Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.

Administrators are advised to monitor affected systems.

Vendor Announcements

Fixed Software

Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via email at tac@cisco.com.

Related to This Alert

Revision History

Affected Products

The security vulnerability applies to the following combinations of products.

Primary Products

Cisco

Cisco Adaptive Security Appliance (ASA) Software

8.4 (.1, .1.3, .1.11, .2, .2.1, .2.8, .3) | 8.6 (.1, .1.1, .1.2)

Associated Products

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